Throughout the world the oceans and atmosphere transport heat from the equatorial regions towards the poles with one remarkable exception that is the South Atlantic Ocean. A consequence of the equatorward movement of heat in the South Atlantic is a large poleward heat transport in the North Atlantic carried by the Atlantic Meridional Overturning Circulation (AMOC). Variability of the AMOC is believed to be a primary mechanism in decadal changes of the North Atlantic surface temperatures which have in turn been implicated with a number of important climate impacts such as rainfall in the African Sahel, the frequency of hurricanes and European weather. The RAPID 26°N array has been measuring the AMOC since 2004. During the period of observation there has been a significant reduction in the AMOC. The change in state of the AMOC is concurrent with other changes in the North Atlantic such as a broadening and weakening of the Gulf Stream, and an altered pattern of sea-surface temperature (SST). These changes resemble the response to a declining AMOC predicted by coupled climate models. The observations provide strong evidence that the AMOC is a major factor in decadal scale variability of North Atlantic climate.